i) Field of the Invention
This invention relates to a method of producing a value product from a source of lime, which may be an industrial inorganic byproduct such as cement kiln dust and minerals having an organic carbon content.
The method exploits heat generated from combustion of the organic carbon, for example, hydrocarbon, content of the mineral and hot combustion gases evolved also provide a source of heat energy which can be recovered.
ii) Description of Prior Art
Oil shale is the name applied (Dietrich and Skinner, Rocks and Rock Minerals, Wiley and Sons) to shales that can contain relatively large percentages of solid organic material that will yield both gaseous and liquid petroleum when the rocks are destructively distilled. Oil shale is a potential source of large quantities of petroleum products, with reported yields as high as 240 gallons/ton of shale for the richest oil shales. More modest deposits have heat values typically of 1000-2000 Btu/pound. Principal typical oxides are silica (50-60% SiO2) and alumina (10-20% Al2O3).
More especially, oil shale is a marlstone-type sedimentary inorganic material that contains complex organic polymers, kerogen, that are high molecular weight solids. The organic kerogen component is a three-dimensional polymer.
Pyrolysis of kerogen forms bitumen, gas and coke and bitumen further pyrolyses to oil, gas and coke and ultimately to carbon. Combustion of oil shale, with excess air or oxygen combusts the hydrocarbons to carbon dioxide and water vapor.
Oil shale is recognized as a potential source of crude shale oil which can be employed as refinery feedstock.
The inorganic marlstone-type component of oil shale typically comprises sandstone, limestone and limonite. Tar sand is the name given to sandstone in which there are relatively large quantities of intergranular, highly viscous, asphalt like hydrocarbon compounds.
More especially, tar sands, also known as oil sands or bituminous rock or sands or asphalt rock, comprise sand deposits impregnated with dense, viscous petroleum. The largest deposits are in the Athabasca area of Alberta, Canada, and in the Orinoco region of Venezuela.
Recovery of petroleum from tar sands is much more costly than well extraction and refining of liquid crude.
Both oil shale and tar sands have potential as a significant source of petroleum where economic processes are valid. Traditionally these processes have required crude oil prices in the region of US $30 to 40 per barrel to justify significant production from these sources. This is because a high proportion of solids have to be handled and heated to recover a barrel of oil.
Cement kiln dust is a byproduct of cement processing and is produced in fine particulate form and is composed of partly and fully calcined calcium carbonate, thus it comprises calcium carbonate and calcium oxide (lime).
Cement plants may produce cement kiln dust (CKD) in differing quantities, even as high as 200,000 tons of cement kiln dust annually, and the CKD represents a disposal problem.
Cement kiln dust has been employed in cement production, but its fineness represents a handling problem and its use is limited by chemistry.
Blast furnace slag is a significant supplementary cement material, however, manufacture of such cement material is limited to slag supplied by iron blast furnaces having slag quenching facilities.
It is an object of this invention to produce a synthetic slag comparable to blast furnace slag and which can be employed as a supplementary cement material, or lightweight aggregate.
It is a further object of this invention to produce such a synthetic slag employing a source of lime, which may be, for example, cement kiln dust; and organic carbon, particularly hydrocarbon, containing minerals such as oil shale and tar sands.
It is still a further object of this invention to provide a method for producing such a synthetic slag, which exploits heat of combustion of the organic carbon, particularly hydrocarbon, content of minerals.
It is yet a further object of this invention to provide such a method with removal of hot combustion gases and recovery of the heat energy of such gases.
It is a still further object of this invention to produce a synthetic slag as described hereinbefore, from the mineral component of oil shales or tar sands, while exploiting the organic component of the oil shales or tar sands, as a source of heat to drive the synthesis reaction.
In accordance with the invention there is provided a method of producing a value product from a source of lime and organic carbon containing mineral comprising: a) establishing an initial melt of an inorganic material providing a source of lime and an organic carbon-containing mineral providing a source of silica, in the presence of a source of alumina; b) adding fresh amounts of said inorganic material, said source of alumina and said organic carbon-containing mineral to said initial melt, c) oxidising the organic carbon content of said mineral in said melt with generation of heat, and exploiting the generated heat in the melting of said fresh amounts to produce an enlarged melt of molten calcium aluminosilicate material, and d) recovering a value product from said enlarged melt.